The truth is we don`t know. The furthest object so far discovered is a galaxy known as EGS8p7 (EGSY-2008532660) which is located in the constellation of Ursa Major in the northern hemisphere. If you search the internet for furthest galaxy discovered, you may get a different answer. I base the statement on the most recent article that I could find on the subject which in this case is the article from Nature World which was written in October 2015. Scientists might find a further galaxy and in which case this article will be obselete.
The galaxy is 13.2 Billion years old and the light has been travelling at light speed since that time. It was born about 500-600 million light years after the big bang occurred, galaxies didn`t just pop into existance, they evolved. However as the universe is expanding, the galaxy will have moved away further from us since then and therefore will be further away than 13.2 billion light years. Theres most likely a galaxy that is even further away from us than that but its light has not reached us. If thats the case, the Big Bang happened a lot earlier than we thought.
According to Universe Today, the observable universe has a diameter of 92 billion light years across. The reasoning for this is the cosmic background radiation which is the left overs of the big bang. When you turn on an untuned television, you see static, that is radiation from the beginning of time.
The universe is expanding at the speed of light ref:Cornell University and light from EGS8p7 will one day disappear from our skies. The galaxy will still exist but any evidence to indicate its existance will have disappeared. There is a theory that if all the light from every galaxy, both local and distant was visible, space would be white not black.
Updated: 09/09/2016 08:45